Centralized traffic control system of the code type for the control of interlocked track switches and railway signals



April 15, 1952 A. L. JEROME E1' Al. 2,592,704

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Pl'll 15, 1952 A. L. JERoME x-:r AL 2,592,704

CENTRALIZED TRAFFIC CONTROL SYSTEM OF' THE CODE TYPE FOR THE CONTROLl 0F' INTERLOCKED TRACK SWITCHES AND RAILWAY SIGNALS Filed Feb. 2s. 194e g-g- INVBNTORS Paiented Apr. 15, 1952 CENTRALIZED TRAFFIC CONTROL SYSTEM OF THE CODE TYPE FOR THE CONTROL OF INTERLOCKED TRACK SWITCHES AND RAILWAY SIGNALS Arthur L. Jerome, Edgewood, Lloyd V. Lewis, Pittsburgh, and Frank T. Pascoe, Carnegie, Pa., assignors to Westinghouse Air Brake Company, a corporation of Pennsylvania Application February 23, 1946, Serial No. 649,598

l 47 Claims. Our invention relates to centralized traiiic control systems for railroads, and more particularly, to railway traiiic controlling apparatus for the control of electrically interlocked track switches and railway signals from a control office.

Our invention is particularly adapted for use in connection with a selective communication system of the code type, such, for example, as the remote control system shown in Letters Patent of the United States, No. 2,229,249, issued January 21, 1941, to Lloyd V. Lewis, or a modification thereof shown in an application for Letters Patent of the United States, Serial No. 496,907, filed July 31, 1943, by Arthur P. Jackel, for Remote Control Systems, now Patent No. 2,411,375, issued Nov. 19, 1946, which system is described in a publication entitled Manual No. 50G-A of The Union Switch and Signal Company, of Swissvale, Pa.

In remote control systems of this type, the components are assembled in the form of individual storage units each identied by a selective code call. Each storage unit in the eld is adapted to control and indicate a group of tralc governing devices, such as a power operated track switch and the railway signals which govern traflic movements over the switch, and is linked, by means of its code call, with a corresponding storage unit in the oiiice control machine which governs the transmission of control codes for governing the operation of the switches and signals in accordance with the positions of their control levers when set into operation by pressing a code starting button to select the code call.

Each oice storage unit also includes a group of indication stick relays which respond to indication codes transmitted by the station storage unit having the same code call, to indicate the condition of the switch and signals of the corresponding group and for also indicating the lcondition of one or more track sections. Furthermore, the system is arranged to transmit the codes one at a time over a single line circuit, without interference, codes originating at the same time, or while the line circuit is in use, being transmitted one at a time in a given order of code superiority.

The principal object of our invention is to facilitate the control of large interlocking plants, particularly of those on multiple track roads where due to the number of track switches involved, the clearing of a signal for a particular route may require the transmission of a series of codes in order to align the track switches controlled by different storage units as required for the desired route.

One object of our invention is to insure that under these circumstances the code for clearing the signal will be the last of the series to be transmitted, regardless of the order of superiority of the different codes, and in this respect, our invention is an improvement upon that disclosed in Letters Patent of the United States, No. 2,343,784, issued March 7, 1944, to Ronald A. McCann and Lloyd V. Lewis, for Centralized Trai-lic Control Systems, and also upon that disclosed in an application for Letters Patent of the United States, Serial No. 623,142, led October 18, 1945, by Arthur P. Jackel, for Remote Control Systems, which issued as Patent No. 2,442,603, on June l. 1948.

Our invention includes improved means for electrically interlocking the switch and signal levers at the ofce in accordance with traokway conditions as reflected by the code controlled indication relays of the communication system, so as to render the control codes transmitted by the various storage units ineffective under certain conditions to change the positions of the switch and signal control relays which they are adapted to control.

A feature of our invention is the provision of a system of route check relays controlled by the signal levers, having pick-up circuits Vcontrolled over a route circuit network conforming to the track layout, by means of which each routel check relay may be energized in response to the reversal of the associated signal lever only if certain of the switch indication relays are energized, thereby indicating that a route governed by the signal which such lever controls is available, and that no conflicting route is established, and further, that the indicated position of each switch of such route corresponds to the last transmitted code for the control thereof. The route check relays govern the transmission of code elements for controlling the track switches in such a manner that a switch control code will contain elements effective to cause the operation of the track switch to reverse or to normal only if .transmitted when the route check relays for all routes over the switch are released. Unless the code is transmitted when the controlling route check relays are released, the switch control elements of the code are of a neutral character to which the switch control relay in the eld is non-responsive.

To include elements for clearing a signal in a code, in response to the reversal of a signal lever, the corresponding route check relay must 'be energized, this relay becoming energized when the signal lever is reversed, over a route circuit prepared by the switch indication relays which cor--` responds to the route established by the track switches. After the corresponding code starting relay becomes energized to store this code for transmission, the route check relay is held energized over a stick circuit, regardless of subsequent switch or signal lever manipulation, until a return indication code is received which indicates that the control relay for the signal cleared by the preceding control code has been restored to its normal position and that conditions in the eld are such that the route may properly be cancelled. Furthermore, the apparatus is arranged so as to insure that any signal which has been cleared cannot be put to stop -by the operation of any lever other than its control lever.

The control code for clearing a signal in any case is capable of being initiated only when a' route governed by the signal is established, as manifested by the energization of the corresponding route check relay. This code may be initiated by the operation of the usual code starting button, after the operator has noted by observation of the indication lamps provided, that the route established is the one desired. In a modication of our invention, means are provided whereby the signal clearing code is initiated automatically, provided the signal lever has been reversed, as soon as the Vroute becomes established as indicated by the closing of the route circuit.

In accordance with another feature of our invention each code controlled signal control relay in the field is restored to normal when a train enters the controlling track section and is thereupon rendered non-responsive to codes for reclearing the signal until a code indicating the occupancy of the section has been transmitted to the ofce, after which the control relay may be reoperated even though the section is still occupied, as required for the clearing of a signal for call-on7 movement, for example. At the oice, the reception of this track occupied indication is effective to prevent the further transmission of code elements for clearing the signal even though the controlling signal lever remains in its reverse position. To reclear the signal, the signal lever must first be restored to normal to correspond with the indicated condition of the signal, and then must be reversed again. One advantage of this arrangement is that it removes any uncertainty which may arise, in the event the transmission of code indica-- tions is delayed for any reason, as to whether the signal control element of a code transmitted at about the time a train is passing the signal should be one for holding it at clear, on the assumption that the train has not yet passed the signal, or should be one for holding the signal at stop, on the assumption that the train will have passed the signal by the time the code is received. Another advantage is that these provisions make it practicable to assign the various steps of the control codes transmitted by any Vstorage unit to the control of wholly unrelated devices, with the assurance that each de-Y vice may be operated at any time by a code which includes steps for controlling other devices, but without causing the undesired or improper operation of such devices.

luminated track diagramV and control panel in `of the indication lamps are normally ute is established, route lamps im,.- and by the route One form of our invention includes a novel ilcheck relays are lighted in the tracks of the diagram, the course of the route being indicated by the lighting of a corresponding series of route lamps.

An optional feature of our invention is the provision of lock indication relays at the ofce controlled by the code system for separately indicating the locked condition of each of the track switches by the lighting of suitable lamps. and for the control of the route locking circuits at'the oflice so as to maintain each route locked after it has been entered by a train until indications are received that the switches of the route are unlocked. In accordance with this feature of our invention the transmission of a code for operating a switch is possible only when the switch is free to respond, and as a train moves through a route, the apparatus for transmitting switch control codes is rendered effective section by section.

One advantage of this feature is that it provides the operator with additional information over that provided by the usual track occupancy lamps which enables him to 'avoid unecessary delays due to attempts to set up routes over switches which remain locked when the detector sections therefor are not occupied, due toy faults in the wayside circuits, for example.

Other objects, purposes and features of our invention `will be pointed out as the description proceeds.

Two forms of apparatus embodying our invention and various modications thereof will now be described, and the novel features thereof will then be pointed out in claims.

Referring to the accompanying drawings, Figs. 1A to 1H, inclusive, show the apparatus located at the control oice, Figs. 2A to 2H, inclusive, together with Fig. 2J show the wayside circuits and apparatus, Fig. 2A also including a plan of the track layout chosen to illustrate our invention, and Figs. 3A and 3B show the station storage units of the communication system for controlling and for indicating the condition of the wayside apparatus. This group of drawings, taken together, illustrates one form of centralized tralic control system embodying our invention, in `which the operators control board, shown in Fig. 1A, is of a conventional type, comprising an illuminated diagram of the track layout of Fig. 2A, together with a series of individual control panels for the several storage units, each of which includes 4one or more control levers and a code starting button and various indication lamps controlled by the code system.

In this form of the apparatus it is to be understood that the code system is that shown in the above' mentioned Jackel application, Serial No. 496,907, employing switch and signal control relays at the stations which are the stick polar type as shown herein in Fig. 3A, and having the station circuits for governing the transmission of indications arranged as shown in Fig. 3B.

Figs. 4A and 4B illustrate a modification employing the communication system of the Lewis Patent No. 2,229,249, in which the switch and signal control relays are neutral stick relays as shown in Fig. 4A, and the circuits for governing the transmission of indications are arranged as shown in Fig. 4B. Each of the forms of our invention may employ either of the two code systems referred to, and when the system of Patent No. 2,229,249 is usedl Figs. 4A and 4B replaV 8 Figs. 3A and 3B in the group of drawings being considered.

Figs. 5A to 5D, inclusive, illustrate a second form of our invention characterized by the provision of a novel form of track diagram having route lamps thereon for indicating the course of the various routes. In this form of our invention, the wayside apparatus is the same as for the first form, the office apparatus comprising Figs. 5A to 5D, inclusive, together with Fig. 1B and Figs. 1E to 1H, inclusive. That is, in this form the control board of Fig. 5A replaces that of Fig. 1A, and the lamp circuits of Figs. 5B, 5C and 5D replace those of Figs. 1C and 1D.

Figs. 6A and 6B, Fig. 7, and Figs. 8A and 8B show further modications of the system of our invention to include therein provisions for indicating the locked condition of the track switches. In this modiiication the indication system includes the circuits of Fig. 6A, for controlling a series of lock indication relays LK, in addition to those of Figs. 1H and 3B or 4B, and the circuits of Fig. 6B replace those connected to wires 3I-34 in Fig. 1H. When this modication is provided in the rst form of the invention, having the control panel of Fig. 1A, lock indication lamps LE are provided as shown therein, controlled as in Fig. '7. In the second form of the invention having the control panel of Fig. 5A, the switch indication lamps are arranged so that they also indicate the switch locking by substituting Figs. 8A and 8B for Figs. 5B and 5D.

Fig. 9 comprises a modification of the route check relay circuits of Fig. 1B and of the starting relay circuits of Fig. 1G, comprising arrangements for effecting the initiation of a code for clearing the signal for a route automatically in response to the indication codes indicating that the route is established.

Similar reference characters refer to similar parts in each of the views.

To simplify the circuits, we have herein shown only the terminals of the sources of current for energizing the various relays, the reference character B designating the positive or supply terminal and the reference character C the negative or common return terminal of the local source of current, in each instance.

The wayside circuits cmd` apparatus Although the system of our invention is well adapted to the control of large and complicated track layouts, a relatively simple one, as shown in Fig. 2A, is deemed sufficient to illustrate our invention. This layout comprises the two main tracks of a double track railroad connected by the crossover switches 3AW--3BW and SAW- 5BW, the lower track also including two single switches IW and 1W. Main line train movements over the tracks of the layout are governed by the high speed signals 2RA and BLA, and other movements by the slow speed signals ZRC, ZRD, 2LA, 2LB, 4R, 6R, and GLC, located as shown. The tracks are divided into sections by insulated joints to form the detector track sections IT, 3T, 5T and 1T, each having the usual track circuit provided with a normally energized track relay ITR, STR, etc. The track relays TR govern the signal circuits of Fig. 2B, the locking circuits of Figs. 2E, 2F and 2G, and also govern the transmission of indications of traiiic conditions to the oiice in the manner shown in Figs. 3B and 4B. The track switches are arranged for power operation by the provision of suitable switch machines ISM, SASM, etc., which are controllable under proper conditions as reflected by the switch locking relays LR of Fig. 2G, by polarized switch operating relays IWZ, 3A-WZ, etc., over circuits arranged as shown in Fig. 2H. Each switch is also provided with a suitable overload relay OR, as shown, these circuits being arranged as shown and described in Letters Patent of the United States No, 2,124,601, issued July 26, 1938, to Norman F. Agnew et al.I for Railwayl Switch Controlling Apparatus.

In Fig. 2H, and likewise in other views involving a plurality of similar sets of circuits only one set of each type is shown in detail. Thus it is to be understood that the circuits for relay 'IWZ, for example, controlling switch 1W, are similar to those for relay IWZ, and that those for the crossover switches 5A--5B are similar to those shown for the switches 3A-3B.

Each switch operating relay WZ in Fig. 2H, is controllable under proper locking conditions by a code controlled switch control relay, such as the relay IWR, Fig. 3A, which is of the stick polar type, or alternatively, by a pair of neutral stick relays such as the relays I NWS and IRWS, Fig. 4A, the switch control relays being controlled by codes which reilect the positions of the corresponding switch levers, such as lever ISW of Fig. 1A or 5A.

Each switch machine such as ISM, 3A--SM or 3B-SM, together with the associated switch operating and control relays IWZ and IWR, or 3A-WZ, 3B--WZ and SWR, as shown in Fig. 2J, controls a polarized switch indication relay or SWP and a normal and a reverse repeating relay INWP and IRWP, or 3NWP and 3RWP. The circuits of Fig. 2J are arranged as shown and described in Letters Patent of the United States No. 2,351,495, issued June 13, 1944, to Arthur E. Dodd, for Electrical Control Apparatus. Each switch repeating relay NWP or RWP when energized indicates that the associated switch or crossover, as the case may be, is locked in the normal or reverse position, respectively, and also that the associated switch operating and control relays are in the corresponding normal or reverse position. The switch repeating relays govern the signal circuits of Figs. 2B and 2D, the locking circuits of Figs. 2E, 2F and 2G, and also govern the transmission of indications of switch position to the ofiice as shown in Figs. 3B and 4B.

Each of the signals of Fig. 2A is to be understood to be of the well-known searchlight type, having a three position mechanism identied by the reference character G prexed by the designation of the signal, and is adapted to cause the signal to indicate caution or slow speed when energized in a normal direction, to indicate proceed when energized in a reverse direction, and to indicate stop when deenergized.

The signal mechanisms G are controlled over a signal circuit network conforming to the track layout and shown in Fig. 2B, to which they are connected by the operation of code controlled signal control relays such as the relays ZRHS and ZLHS, etc., of the polar stick type, shown in Fig. 3A, or alternatively, by the similarly designated relays of the neutral type shown in Fig. signal control relays such as the relays ZRHS being controlled by codes which reflect the position of the corresponding switch lever such as lever ZSG of Fig. 1A or 5A, provided the corresponding route check relay ZRGS or ZLGS of Fig. 1B is energized.

As will be clear from Fig. 2B, only the signal mechanisms ZRAG and SLAG are arranged for rent supplied thereto being controlled by theV relays ZSHP and 22HP respectively, which relays are controlled in the conventional manner by the signals in advance of signals 2BA and ELA, by means notshown.. Signals 2RC and SLC are arranged to be governed by the code controlled relays 2COS and SCOS, Fig. 3A, to serve as call-on signals toadmit trains to the main line routes when occupied.

The signal control relays 2RHS and @RHS also control a repeating relay 2'-lI-ISP, shown in Fig. 2D, which governs the route circuits of Fig. 2B as required in connection with the provision of the intermediate signal BR.

Each signal mechanism G of Fig. 2B controls a stop indication repeating relay ZRGP, ZLGP, etc., shown in Fig. 2C, which relay is energized only when the signals of the corresponding group indicate stop. Each signal repeating relay such as IRGP or ZLGP together with the associated signal control relay ZLHS or ERHS controls an approach locking stick relay ZRAS or 2LAS, shown in Fig. 2E, in the manner described in the above mentioned McCann et al. Patent No. 2,343,784, and the clearing of each signal is made dependent upon the release of the associated approach locking relay. As will be clear from Fig. 2E, each approach locking relay such as relay 2RAS is released by the associated signal control relay 2RI-IS, when the latter is operated to prepare a circuit for clearing a signal. The release of the approach locking relay is checked by including a back contact thereof in the signal circuit, as illustrated in Fig. 2B, for example, by back contact b of relay ZRAS in the circuits for each of the mechanisms RAG, ZRCG'and 2RDG. The opening of front contact o of relay BRAS prevents the clearing of the opposing signal for the established route, such as signal ZLA, by disconnecting terminal B from the route circuit for its mechanism ELAG.

The signal repeating relays RG?` and LGP and the approach locking relays RAS and LAS also govern the transmission of signal indications by the code system as shown in Figs. 3B and 4B, so as to indicate whether the signal for the established route is at clear'or at stop, and if at stop, whether or not the associated approach locking relay is energized.

Fig. 2F shows a series or directional stick relays ES and WS, designated section locking relays, which are controlled by the approach locking relays of Fig. 1E' and co-operate therewith in the control of switch locking relays LR.

As shown in Fig. 2G, a switch locking relay LR is provided for each switch section. Each relay LR, when released, locks the switches in the corresponding section by opening the circuits for the switch operating relays WZ of Fig. 2H, and also opens the circuits for the switch control relays WR of Fig. 3A or for the corresponding relays NW'S and RWS of Fig. 4A. Each such relay LR is held released by the track relay TR for the corresponding section to provide detector locking when the section is occupied. Relay lLR, for example, when released, locks switch IW and also the crossover switches SAW and SBW, the latter being also locked by relay LR when released.

When a signal control relay RHS or LHS is operated, the release of the associated approach locking relay RAS or LAS releases the locking y relay LR for the first section of the established route, and also releases one or more of the sec-V 8,. tion locking relays of Fig.'2F,whic'h serve to release the locking relays LR of the succeeding sections of the route and to hold them released until the train occupying the route reaches the corresponding sections and the detector locking becomes eiective.V Considering the route from signal 2RA to signal ZLA, for example, it will be seen that relay ILR is released to lock the switches in section IT by the opening of contact d of relay ZRAS, and that the opening of contact c of relay ZRAS releases relay IES. Since contact c of relay 3RWP is open, the opening of contact c of relay IES releases relay ILR to lock the switches in section 1T. If, however, the route from signal ZRC to signal 6R is set up, contact f of relay 3NWP Vis open and the opening of Contact b of relay IES releases relay 3LR, and relay ILR is not released.

When a train enters Veither of the routes mentioned, relay ITR releases to hold relays ILR.

and IES released, and by opening its contact y,

Fig. 3B, releases a repeating relay ITKR. The closing of back contact e of relay ITKR, Fig. 3A, restores the signal control relay ZRHS to normal, opening its contacts a. and c, in the cir'- cuits for mechanisms 2RAG and ZRCG shown in Fig. 2B. If signal 2RC has been cleared, this restores the signal to stop and causes relay ZRGP, Fig. 2C, to become energized. If signal ZRA has been cleared, it is put to stop by the opening of contact b of relay ITR, in the circuit for mechanism ZRAG, the release of which energizes relay ZRAGP, Fig. 2C, and thereby energizes relay ZRGP. Relay 2RAS, Fig. 2E, then picks up over Y back contact c of relay ITR, and is held energized over its own front contact a after section IT is vacated. Relay IES holds relay ILR or BLR released so long as the train occupies section IT, relay ILR becoming energized when the train vacates section IT, while'relay 'ITR or STR, as the case may be, will hold relay 'ILR or 3LR released until the second section of the route is vacated, each locking relay LR becoming energized when the train vacates its section.

When a signal is restored manually to stop by the operation of its control relay RHS or LHS to normal, the reenergization of the approach locking relay LAS or RAS is delayed for a suitable time interval by the operation of a time element relay such as relay 2LTE or 2RTE, Fig. 2E, which provides time or approach locking in accordance with the usual practice.

The code communication. system It has already been pointed out that the centralised trac control system ofY our invention may employ either of two code systems, that of application Serial No. 496,907, of which the field storage units are illustrated in part in Figs. 3A and 3B, or that of Patent No. 2,229,249 of which the corresponding portions are shown in Figs. 4A and 4B. Both systems employ substantially similar apparatus at the oice for governing the character of the control codes transmitted from the office and for controlling the indication relays which register the character of the received codes and Figs. 1F, 1G and 1H, showing these portions of the system, may therefore be taken to represent either system. For an understanding of our invention, it is deemed suicient to point out that either of the communication systems mentioned may be arranged to provide-seven code steps or channels, for the intermittent transmission of controls from the office to a selected storage unit in the field. as well as seven other channels for the transmission of indications from any of the field storage units to the oilice. The control channels are identied herein by the numbers I to 1, inclusive, and the indication channels by the numbers 9 to l5, inclusive. For simplicity, the code channels are represented herein by direct wire connections, such as would be used for the control and indication of apparatus in the vicinity of the control office, although the coding apparatus establishes the channels only one at a time over a single line circuit, but this may be disregarded and the operation may be more readily traced by assuming that terminals I to 1, in Fig. 1F, extend directly to terminals I to 1, in Fig. 3A or 4A, and that terminals 9 to I5, in Fig. 4A or 4B extend directly to terminals 9 to I5 in Fig. 1H. Terminal 2 represents an idle channel, not used herein, and channel I4 is used only in the modification shown in Fig. 6A.

Each control code transmitted from the office is initiated by the energization of a starting relay such as relay OIST, Fig. 1G, of which one is provided in each office storage unit. Each starting relay may be energized by the operation of a starting button ISTB in the corresponding panel and when energized completes a starting circuit including its contact c to effect the initiation of the corresponding code as described in Patent No. 2,229,249. Each control code includes a dis- Y tinctive code call by which a selector relay such as relay OIS, Fig. 1F, in the oice storage unit and a delivery relay such as relay ID, Fig. 3A or 4A, in the corresponding field storage unit, are energized, to establish channels I-'I to position a particular group of control relays at the station in accordance with the condition of energization of the channels as determined by the positions of the levers of the corresponding office panel. The manner in which the various functions have been assigned to the different code steps or channels and to the different panels and storage units will be obvious from a consideration of Figs. 1F and 3B.

In the code system of application Serial No. 496,907, the indication codes are initiated by the release of normally energized starting relays such as the relay IST, Fig. 3B, in the station storage unit. Relay IST is released in response to a change in position of any of the indicating relays which govern the unit, and also when the delivery relay ID is operated by a control code. A return indication code therefore follows each control code, regardless of whether or not the positions of the controlled devices are changed. Each indication code includes a distinctive code call by which a selector relay, not shown, and a repeating relay, such as relay IMSP, Fig. 3B, in the station storage unit, and also a delivery relay OID, Fig. 1H, in the corresponding office storage unit, are energized to establish the indication channels 9-I5, and thereby effect the selective energization of the indication stick relays INWK, IRWK, etc. of the oiiice unit in accordance with the condition of energization of the channels as reflected by the positions of the indicating relays assigned to the corresponding station storage unit.

In the system of Patent No. 2,229,249, as illustrated in Fig. 4B, the circuits for energizing the channels 9-I5 are similar to those above described, only one of the relays MSP being shown, for simplicity, but the starting circuits are differently arranged. In this system the starting relay IST is normally deenergized, and is picked up by relay ID, or by any indication relay which changes its position, over a circuit which as shown is in most instances a branch of the circuit by which the corresponding one of the channels 9-I5 is energized. At the end of each indicating code a control relay VC in the station unit is momentarily energized, and connects the pickup circuits for a series of stick relays 9-IIV, IUV, etc., to the correspondingly numbered channels 9, I0, II, etc., and at the same time opens the stick circuits for these relays, as shown and described in the patent. It is to be understood that when relay VC operates, the relays V are actuated to their energized or released positions as required to open the circuit for the starting relay, provided the positions of the indicating relays at the station did not change during the transmission of the code and correspond with the positions -to which the office indication relays have been operated.

The o'ice circuits and apparatus for governing the code system The transmission of control codes is governed in accordance with wayside conditions by the indication relays of Fig. 1H as well as by the control levers, and referring to Figs. 1II and 3B, it will 'be seen that the relays controlled over channels 9 and II such as relays INWK and IRWK, are normal and reverse switch indication relays which reflect the position of the corresponding track switch IW and of the control and operating relays IWR and IWZ therefor. Each normal or reverse switch indication relay is adapted to be picked up by code over channel 9 or II, and is held energized locally after the termination of the code by a stick circuit extending from terminal B at its front contact a, over a back contact of the delivery relay through its winding to terminal C at contact b or d of the associated switch lever, such as lever ISW, provided the lever position corresponds with the indicated position of the switch. If the switch lever is moved to its opposite position, the circuit for the energized indication relay is extended to include back contact d of the associated code starting relay, such as relay OIST, so that when the starting relay is operated to initiate a code for changing the position of the switch, the energized indication relay is released to cancel the switch indication. Thus the normal indication relay NWK is released by a switch reverse control code, andv the reverse indication relay RWK by a switch normal control code, and the energization of either of these relays indicates the switch position registered by an indication code which followed the last transmitted control code for operating the switch. In this respect the circuits function like those of the McCann et al. Patent No. 2,343,784, hereinbefore referred to, but as shown herein, in Fig. 1H, and also in part, in Fig. 6B, they are modified in accordance with a feature of our invention by the provision of additional connections from the left-hand terminals of the windings of relays NWK and BWK over contacts b or d of the associated switch levers, front contacts d of the associated starting relays ST and wires 3|, 32, 33 and 34 to terminal C at the front contacts e or f of the route check relays RGS or LGS. The circuits which control the route check relays RGS and LGS are shown in Fig. 1B, and the circuits which include their contacts e and f, as shown in Fig. 1H or 6B, constitute a novel arrangement for insuring that the energized indication relays for the energized.

In Fig. 1F, back contacts c of the switch indication relays 'are included in the circuits over which the switch control channels I and 3 are energized in accordance with the positions of the contacts a of the switch levers, so that a cancellation of the switch indication is necessary in order -to render the switch control elements of a code eiective to change theV position of the switch control relay'WR, Fig. 3A, which such elements govern. Otherwise channels I and 3 are both deenergized in a code transmitted when a switch lever and its control relay WR occupy dissimilar positions, and relay WR is not operated. This is also true of the neutral switch control relays INWS and IRWS of Fig. 4A, the circuits for which differ from those for the similarly designated relays or" Patent No. 2,229,249 in that relay INWS is not releasedV by 'a control code unless channel 3 is energized, nor is relay IRWS released unless channel I is energized.

Referring now to Fig. 1B, it will be seen that front contacts b and d of the switch indication relays are so interconnected that' when closed e they form route circuits, there being one such circuit conforming to each route through the A track layout of Fig. 2A. It will also be seen that when any signal lever such as lever 2G is operatedV to its right-hand or left-'hand reverse position, with a route circuit established, the corre- Y sponding route check relay ZRGS or ELC-S is connected to the route circuit over the signal lever Contact b or d and becomes energized and in turn holds energized the switch indication relays for the switches of the corresponding route. It follows that the energization of channel I or 3 to Y, operate a track switch away from its existing .position is possible `only when the route check relay for each route over the switch is released.

Visual indications of the condition of the switch indication relays are provided Yin the control board of Fig. 1A by lamps such as INE vand IRE mounted above the switch levers and energized over contacts e of the switch indication relays as shown in Fig. 1D. Whenthe control board of Fig, 5A is used, these lamps are mounted in the track diagram andare controlled bythe route check relays as shown in Fig. 5B or 8A so that they are lighted to indicate the course ofV an established route and are consequently not available to indicate the response of a track switch to a switch control code received when the route check relays are released; In Fig. 5A, a red lamp such as lamp IWE is mounted above each switch 'lever which is lighted by the operation of the cirl cuits of Fig. 5D or 8B when the switch lever is out of correspondence with the indicated positionof the switch. The switch indication relays also have contacts or selecting purposes in the circuits for the signal indication lamps on the track diagram, shown in Fig. 5C, in this form of the apparatus.

Considering nowrth-e remaining indications relays of Fig. 1H, the relays iTK, STK, etc. are trackindication relays controlled'over channel I0 to light red lamps ITKE, etc., in Vthetrack diagram, to indicate when the corresponding track sections are occupied,V thelainp circuits being shown in Fig. 1E. Storage of the detector section indications is provided, and Whernfor example, the track relay I TR of Fig. 2A releases, it opens its contacts g and h, Fig'. 3B, to release a repeating relay ITKR and a storage relay ITKS, and these relays in turn release the starting relay IST of the station storage unit to initiate the transmission of an indication code in which channel I 6 is Venergized over back contact d of relay ITKS to energize relay ITK and light lamp ITKE. Relay IST remains released until after the indication lcode which itecontrols is initiated, Vand by opening its left-hand cont-act IJ, relay IST holds relay ITKR released until relay IST `is reenergized, while the opening of contact b of relay I TKR holds relay I TKS released until after the code is initiated'and relay IMSP is thereby energized, after which relay I TKS isrheld released by relay IMSP until the code indicating the occupancy of the controlling track section IT is fully transmitted, and also'by relay ITR until the section is vacated.V It'will be seen that in accordance with this arrangement the track occupied indication is stored by relay ITKS to insure its til after'sectionY IT has been vacated.

In the alternative form of Fig. 4B, the indicaftion of the occupancy of the detector sections,

spending approach sections by lighting of track diagram lamps such as lamp ZRAE, Fig. 1E, and

also by the momentary sounding of a bell X, shown in Fig. 1H. Relay POK is a power off indication relay controlled over channel I2 by a relay POR, Fig. 3B, which relay is normally energized by connections to terminals BX and CX of the primary source of power at the station. The release of relay POR indicates the loss of the primary power supply by the lighting of lamp POE of Fig. 1H, and by the operation of a buzzer BZ, controlled by a stick relay BR so that the buzzer continues to sound following the energization of relay BR until acknowledged by the operation of a key BK. Y

The relays controlled over channels I3 and I5 are signal indication relays controlled by the signal repeatingV relays RGP and LGP of Fig. 2C and by the approach locking relays RAS and LAS of Fig. 2E. Relay ZRHK in Fig. 1H, for example, is energized, and relay ZLHK is held released by the release of relays ZRGP and ZRAS when one of the signals 2RA, 2RC or 2R13 isV cleared, and in Fig. 3B, terminal B at back contact e of relay ZRAS is connected to channel I5 over back contact c of relay 2RGP or front contact c of relay ZLGP, but is disconnected from channel I3 by the opening of front contact c of relay ZRGP. Similarly, relay ZLEIK is energized, and relay 2RI-IK is held released by the release of relays 'LGP and ZLAS, when signal ZLA or 2LB is cleared. The stop signal indication is thus transmitted by deenergizing both channels I3 and I5, and the clear'signal indication by energizing one or the other. In addition, a distinctive approach locked indication may be transmitted by energizing both channels I3 and I5, as occurs, for example, when-relay ZRAS or ZLAS is released 4and the, signal fails to clear, or when a signal is returned manually to stop and the approach locking relay remains released. The clear signal indications are displayed by steadily lighting a green lamp such as 2LE or 2RE which in Fig. 1A is mounted above the signal lever and controlled as in Fig. 1C, and as shown by the circuits, these lamps are arranged to be energized at times over the contacts of a continuously operating interruptor relay CT so as to flash periodically, to indicate the energization of the associated route check relays ZRGS and ZLGS. In Fig. A, the green lamps, such as ZLE and ZRE, are mounted on the track diagram and controlled as in Fig. 5C, and the flashing indications are not provided in view of the fact that the lamps of Fig. 5B indicate the condition of the route check relays. The stop indication is displayed by steadily lighting, and the approach locked indication by flashing, a red lamp ZNE mounted above the signal lever. In Fig. 1C lamp ZNE is normally energized, While in Fig. 5C, it is normally dark, its circuit being open at contact e of the signal lever when this lever occupies its normal position.

The signal indication relays RHK and LHK also govern the route check relays RGS and LGS of Fig. 1B and the call-on relays COR of Fig. 1F, as hereinafter described.

In the alternative code system of Fig. 4B, channels I3 and I5 are similarly controlled, but the circuits diier from those of Fig. 1B principally in the provision of relays I3V and IEV which pick up or release in response to the transmission of a code to govern the circuit for the starting relay IST as explained in Patent No. 2,229,249.

Channel I4 is used only inthe modication of Fig. 6A, Where a series of lock indication relays LK are controlled over this channel to indicate the condition of the switch locking relays LR of Fig. 2G.

In each form of our invention a code indicator relay such as ICK, Fig. 1G, is provided in each oflice storage unit, which is picked up by the starting relay of the unit whenever a control code is stored for transmission by the unit, and is held energized by the associated delivery relay OID until a return indication code is received. During this period, a code indicator lamp ICKE is lighted by relay ICK. These lamps provide additional information as to the operation of the system of value to the operator, particularly in cases in which a control code is followed by a return indication code indicating no change in the positions of the controlled devices. The relays CK also govern the transmission of signal control codes as will now be described.

It has already been explained that code elements effective to operate a track switch are transmitted only'when each route check relay of Fig. 1B which governs a route over the switch is in its released position, and that each such relay ZRGS or ZLGS becomes energized in re spense to the reversal of the associated signal lever ZSG, provided a route circuit is established in Fig. 1B, for a route governed by a signal which such lever controls. If the route check relay becomes energized, as indicated by the flashing of the signal indication lamp 2LE or ZRE in Fig. 1A or the lighting of a series of route lamps in Fig. 5A, a signal clearing code may be initiated by operating the associated starting button and relay CK then disconnects the energized route check relay from the route circuit but holds it energized over a stick circuit as shown in Fig. 1B. In the rst form of the apparatus, contact e of 14 relay ICK, Fig. 1C, opens to discontinue the ilashing of the signal indication lamp.

When this control code is transmitted, channel 5 or 'I is connected to terminal B as shown in Fig. 1F, over the left-hand or right-hand contact a of lever ZSG, back contact a or b of a relay ITKA, hereinafter described, and front contact d of relay 2RGS or ZLGS, causing the signal control relay ZLHS or ZRHS of Fig. 3A to assume its reverse position to elect the release of the approach locking relay and the clearing of the signal as already described.

Assuming that relay ZRHS has been reversed, for example, the return indication code by which relay ICK is released causes relay ZRHK to become energized to maintain relay ZRGS energized over its stick circuit after relay ICK releases. That is to say, if relay ZRHS reverses, relay ZRAS releases, and the return indication code will indicate either the clear or the approach locked condition of the signal by energizing relay ZRHK alone or along with relay ZLHK, as already explained.

It will be seen therefore that after a signal clearing code for reversing a signal control relay such as ZRHS has been stored for transmission, the route check relay ZRGS is locked energized, and can be released only after an indication code has been received which indicates that relay 2RHS has been restored to its normal position. The route check relay when energized maintains the route circuit established by reason of the connections to wires 3I-34 in Fig. 1H, to prevent a change in route, and is releasable onlyl when it is proper t0 change the route, since the code Which indicates that the signal control relay is in its normal position also indicates that the signals such relay controls are at stop and that vtheir appreach locking relay is energized.

Centralized traic control systems of the type shown usually include a maintainers call signal, and this is provided herein by controlling a polar stick relay MCR, Fig. 3A, over channel 4 by which the operator may light a lamp E by reversing a lever MC, Fig. 1F. This lever is assigned to the storage unit having the starting button ISTB, but for convenience lever MC is of the push-turn type, having an auxiliary contact a connected in multiple with the contact of button ISTB, which contact closes momentarily to energize the starting relay OIST whenever Contact c of lever MC is moved from one operative position to the other.

Each control code initiated by the operation of lever MC Will therefore include elements for the control of switch IW and also for the control of the signals governed by lever ZSG. It is obvious that switch controls cannot be issued improperly by the operation of lever MC and this is also true of the signal controls, due to provisions which will now be described.

Assuming that relay ZRHS has been reversed by the energization of channel l, to clear one of the signals which relay ZRHS controls, for an approaching train, if lever 2SG is not moved from its right-hand position, channel 'I will be energized in each succeeding code transmitted by the same unit prior to the time the train enters section IT, thereby maintaining relay ZRHS reversed to hold the sign-al at clear until the train passes it.

When the train enters section IT, relays ITKR, ITKS and IST, Fig. 3B, are released by relay ITR to initiate the transmission of a track occupied indication code, as already described. The closing of back contact e of relay ITKR energizes the energized.

lower winding of relay ZRHS, restoring relay ZRHS to normal. Relay ITKR remains released from the time section IT becomes occupied until a code indicating its occupancy is transmitted, and the dropping of contact d of relay ITKR prevents the energization of the upper winding of relay ZRHS in a direction tending to reverse relay ZRHS, in the event control codes are received with channell energized, during this period.

When the track occupied indication is trans mitted, relay ITK becomes energized to light lamp ITKE as already described, since relay ZRHS has been restored to normal, and this code will be effective to release relay ZRT-1K to indicate the return of the signal to stop. When relay ITK is first energized, a circuit is closed momentarily from channel I0, Fig. 1H, over back contact b of relay ITK and front contact g of relay ZRGS to wire 2 I, and thence in Fig. 1F, through the upper fwinding of relay I-TTKA to terminal C. Relay I-TITKA therefore picks up and establishes a stick circuit at its front contact b extending to terminal B at the reverse contact o', of lever 2SG and disconnects contact a of lever ESG from channel 'I, remaining energized only until lever ZSG is restored to normal. Relay ITKR is released upon the transmission of the track occupied code, rendering relay ZRHS operable to reverse by control codes in which channel 'I is YIt follows that the energization of the signal control channel or 7 in a transmitted code cannot occur inadvertently, due to a failure of the operator to return the signal lever to normal` after the signal it controls has been put to stop by a train.

Each of the slow speed signals in Fig. 2A, that is, each signal except 2RA and BLA, may be operated as a call-on signal to admit a train to an occupied block, but to clear signal 2RC or LC for the route governed by signal ZRA or BLA when such route is occupied, the operation of a call-on button such as 2CD is required. As will be clear from Fig. 1F, when signal lever ZSGVis in its right-hand position with relay I-ITKA released, to enable channel 'I to be energized, a

call-on relay ZCOR may be energized by Ypressing' button 2CO to connect terminal B at contact b of relay COR to channel 6, whereby relay 2COS, Fig. 3A, is operated to reverse along with relay ZRHS when the signal clearing code is transmitted. Relay ZCOR is released by relay ZRHK in response to a code indicating the clearing of the signal, and it follows that channel S is not energized in any following control code. Relay COS, however, being of the stay-where-put type, remains reversed until relay ZRHS is restored to normal, whereupon it is restored to normal by the energization of its lower winding over a. circuit controlled jointly by relays 2RHS and ZRHSP as shown in Fig. 3A. It follows that a separate operation of the call-on button as well as of the signal lever is required for ,each train movement.

Referring now to the alternative coding equipment of Figs. 4A and 4B, it will be seen that this is also arranged to prevent the inadvertent clearing of signals as described above. Thus in Fig. 4A, if channel l is energized, relay ZRHS is maintained energized by each control code received prior to the release of the detector track relay ITR. When relay ITR releases, a circuit is closed momentarily by relay ITR and a repeating relay ITP to pick up relay ITSA, Fig'. 4B, along with relays IOTS and IST. Relay ITSA is held energized over a stick circuit by relay IST until the 16 ltrack occupied code is transmitted. Relay ZRHS is released by the opening of contact lc of relay ITR, Fig. 4A, and is held released by the opening of contact b of relay ITSA only until the track occupied code is transmitted. Likewise, relay ZCOS in Fig. 4A is energized over channel 5 and is then held picked up by relay ZRHS until the latter relay is released.

It will be seen that in view of the provisions describedV above the various controlled devices may be assigned to the dilerent storage units in any desired order or combination, without interfering with their proper operation. Thus a unit may control two independent switches and a group of signals, or two groups of signals, or may control other devices as illustrated by the maintainers call signal shown.

Operation The operation of the system of our invention Vwill now be described under different Iassumed conditions, considering rst the form employing the control panel of Fig. 1A, the cnice circuits of Figs. 1B to 1H, inclusive, and the field circuits of Figs. 3A and 3B for controlling the wayside ap-V paratus of Figs. 2A to 2H, inclusive, and-of Fig. 2J. Y Starting with this apparatus in its normal condition, as shown, it will be rst assumed that the operator reverses the switch lever SSW and presses button BSTB, to reverse the crossover switches 3AW-3BW, and when the switch indication lamp SRE becomes lighted indicating that the route from signals 2R to GR is established, he moves the signal leverV ZSG to the right and presses button ISTB, to clear signal ERC, for a train movement over that route. Y

The operation of button 3STB energizes the starting relay OSST, Fig. 1G, thereby initiating the transmission of a control code and also energizing relay SCK to light the code indicator lamp 3CKE. The VVopening of back contact d of relay ,O3ST, Fig. 1H, releases relay 3NWK and so extinguishes lamp 3NE, and by the resulting code, relay 03S, Fig. 1F, is energized to connect terminal B at its contact f over the reverse contact a of the switch lever 3SW and back contact c of relay 3NWK to channel 3. In Fig. 3A, the delivery relay 3D is energized to extend channel 3 over its contacte through the lower winding of relay SWR to terminal C over contacts e'of the switch locking relays ILR and SLR provided the proper traffic conditions prevail as manifested by the energization of these locking relays.V

It will be seen that relay 3NWK upon releasing opens the route circuit in Fig. 1B, for the existing route from signal 2R to 2Ll at its contact d, and thatV the operation of the interlocked circuits of Figs. 1B and 1H is such as to require the levers and starting buttons to be operated in the sequence recited'above. Thus if lever 2SG is reversed before button SSTB is operated, relay ZRGS, Fig. 1B, will be energized over the route circuit extending to terminal B at back contact c of relay ZLGS, causing the green lamp 2HE to flash, indicating that the existing route cannot be changed. VIf the operator should then press button"3STB, leaving relay SSW reversed, the

The operator, however, may move lever ZSG to the right after relay SNWK releases, but. relay ZRGS will remain released until the new route is established and indicated. During this period channel I is disconnected from contact `a of lever 2SG, Fig. 1F, by the open contact d of relay ZRGS, and relays ZRHS and ZLHS would be retained in their normal position in response to a control code transmitted from this panel. Since relay INWK is held energized over the normal contact b of lever ISW, it would not release if button ISTB were operated. It follows` that the operator is free to initiate a control code by operating relay OIST at this time, to control the maintainers call signal over channel 4, or for any other purpose independent of the switch Iand signal levers assigned to the same unit.

Assuming now that relay EWR has been reversed by the proper manipulation as hereinbefore described, the normal switch repeating relay 3NWP, Fig. 2J, is released by the reversal of contact b of relay 3WR, Iand the reversal of contacts a and c of relay SWR causes relays .3A-WZ and 3B--WZ to assume their reverse positions in which the motors of the switch machines are energized over circuits similar to that shown for switch machine I-SM, in Fig. 2H, to operate the crossover switches 3AW-3BW to reverse.

The operation of the delivery relay 3D by this code also releases the station starting relay 3ST by the opening of its back contact j, as shown for relay ID in Fig. 3B, thereby initiating the transmission of a return indication code which indicates the transit or open condition of the crossover switches, channels 9 and II being deenergized to maintain relays BNWK and BRWK released. The operation of relay 03D by this code, however, releases relay 3CK and by extinguishing lamp SCKE, indicates the response of the wayside apparatus to the switch control code.

When switches 3AW-3BW are operated and locked reverse, relay 3RWP becomes energized as shown in Fig. 2J, and initiates an indication code in which channel I I is supplied with current over its contact d, Fig. 3B, thereby energizing relay SRWK, Fig. 1H, over the reverse contact d of lever SSW, and causing the reverse switch indication lamp SRE to become lighted, while the closing of contact b1 of relay SRWK in Fig. 1B prepares route circuits over which relay ZRGS or LGS may be energized. Assuming that lever ZSG is operated to the right, relay 2RGS will become energized over the circuit from terminal B at back contact b of relay ZLGS or at front contact lc of relay NWK, back contact b of relay SLGS, contact c of lever ZSG, front contacts b of relays 3RWK and INWK, contact b of lever 2SG, and back contacts b of relays ICK and ZRI-IK through relay ZRGS to terminal C. The energization of relay ZRGS is made manifest to the operator by the flashing of lamp 2RE, and after noting from observation of the switch indication lamps that the route established is the one desired, he presses the starting button ISTB to initiate a code for clearing the signal controlled by the reversed lever ZSG.

The apparatus of our invention may also be arranged that the code for clearing the signal is transmitted automatically following the last of the indication codes by which the route circuit is established, provided the signal lever is reversed. In this modication the circuits for each of the route check relays, such as relay ZRGS are arranged as illustrated for that relay, in Fig. 9. Referring now to Fig. 9, and assuming that lever ZSG is in its right-hand position, relay OIST picks up over a route circuit such as the one extending from terminal B over contact d of relay SNWK and contact b ofrelay INWK for example, thence over the right-hand contact b of lever ESG, back contact f of relay ICK, back contact g of relay ZRHK, back contact 7 of relay ZRGS, the normally closed contact a of button I STB and the continuity-transfer contact a and winding of relay OIST to terminal C. Relay IRGS is energized at the same time over back contacts b of relays ICK and ZRHK, but is somewhat slower to pick up so that it does not open its contact a' until front contact of relay OIST closes to establish the usual stick circuit for relay OIST. Relay OI ST is thus operated automatically to initiate the signal code, with the same eiect as if button ISTB had been operated following the energization of relay 2RGS.

In either case, relay OIST when energized picks up relay ICK, which extinguishes lamp ZRE and lights lamp ICKE, and disconnects relay ZRGS from the route circuit and holds it energized over the stick circuit including front contact b of relay I CK and front contact a of relay ZRGS. The energization of relay OIST also initiates the transmission of a control code by which relays OIS and ID are operated. Switch lever ISW is assumed to be in its normal position and consequently channel I is energized in this code and relay I WR of Fig. 3A,` which is aS- sumed to be in its normal position, is `energized over contact a of relay ID, in a direction to hold it in that position. Relay IWR cannot be operated to reverse in response to the7 reversal of lever lSW, for the reason that channel 3 is dis.

connected from lever ISW at back contact c of relay INWK, Fig. 1F, and as shown in Fig. 1H, relay INWP is held energized over a stick.l circuit having a connection to terminal C at front contact e of relay ZRGS, provided lever ISW is reversed and relay OIST is operated after relay 2RGS becomes energized.

Channel I is now connected to terminal B at the right-hand contact a of the signal lever ZSG, Fig. 1F, back contact b` of relay ITKA. front contact d of relay ZRGS, and contact g of relay OIS, energizing relay iP, Fig. 3A, so that the, signal control relay ZRHS is energized reverse over contact g of relay ID. Relay ZRHSP, Fig. 3A, and 2-4I-ISP, Fig. 2D, become energized over the reverse contacts d and b, respectively, of relay ZRHS, and the approach locking relay ZRAS, Fig. 2E, is released by the opening of the normal contact b of relay ZRHS. Relay ZRAS releases the switch locking relay ILR, Fig. 2G, and also the section locking relay IES, which releases relay 3LR. The switch locking relays LR upon releasing open the circuits for the switch control relays IWR and SWR, Fig. 3A, and for the corresponding switch operating relays WZ of Fig. 2H, to lock the switches of the established route. The closing of the back contacts of the relays LR completes a circuit for the signal mechanism ZRCG, Fig. 2B, which extends from terminal B at front contact a of relay 2-4HSP over back .contact g of relay 3LR, front Contact a of relay gized in the reverse direction to display a slow speed, or yellow indication, releasing relay ZRGP, which by opening its contact a in Fig. 1E holds relay ZRAS released until the signal is restored to st op.

' The operation of relay ID by the signal clearing code releases the starting relay IST, Fig. 3B, to initiate a return indication code. In general, relay ZRGP will have released before the thirteenth step of this code is reached, in which case channel I3 is not energized, but channel I5 i's-energized by relay IMSP over back contact e of relay 2RAS and back contact c of relay ZRGP, or front contact c` Vof relay ZLGP, the operation of relay OID by this code energizing the signal indication relay ZRHK, Fig. lI-I, and releasing relay ICK. Lamps ICKE and 2NE are extinguished, and the green signal indication lamp ZRE in Fig. 1C is steadily energized over back contact e of relay ZLHK and front contact e of relay 2RHK. Relay ZRGS is held energized after the release of relay ICK, over front contact b of relay 2RI-IK.

In the event the signal fails to clear in time to release relay ZRGP before the thirteenth step of this code is transmitted, channels I3 and I5 will be energized, being connected to terminal B at back contact e of relay ZRAS in Fig. 3B over the front contacts c of relays ZRGP and ZLGP, respectively, so that the indication code will cause relay 2LHK to become energized along with relay ERI-IK, releasing relay ICK and extinguishing lamps ICKE, and completing a new circuit for lamp ENE in Fig. 1C extending over front contacts c ofV relays ZRHK and ZLHK to terminal B at the contact of the interrupter relay CT, thereby indicating the approach-locked condition by the display of a flashing red indication by lamp ZNE. If the delay in the clearing of the signal is but a temporary one, a second code is initiated Y upon the release of relay ZRGP, by which relay ZLI-IK is released and relay ZRHK is held energized, whereby lamp ZNE is extinguished, and lamp ZRE is steadily lighted to display the signal clear indication as already described.

Y It will be seen therefore that the route check relay, such as relay ZRGS, is maintained energized after the starting button is operated to initiate a signal clearing code for reversing the signal control relay 2RHS, until an indication code has been received in which channels I3 and I5 are open, to release relays 2RHK and ZIJ-IK, thereby indicating that the signal control relay occupies its normal position, the signals it controls are at stop, and the approach locking relay 2RAS controlled thereby as well as the associated relay 2LAS are both energized. The release of relays ERI-IK and ICK by this code reconnects relay 2RGS to the route circuit, and it may then be released by restoring vthe signal lever ZSG- to its normal center position. It follows that in order to cancel a route Vafter the issue of a signal clearing code, the release of the route check relay such as relay ZRGS, may be effected by transmitting a signal stop code, with the signal lever in its normal position, to restore relay 2RI-IS to normal and Vthereby reenergize relay BRAS. Under certain conditions, time locking apparatus as illustrated by relay ZRTE in Fig. 2E, will delay the reenergization of relay ZRAS for a suitable interval, but in any case, relay ZRGS will be released by the indication code. transmitted when relay 2RAS picks up, if lever 2SG is normal, as is ob'- vious.V Y

In prior .systems employing route circuit netthese switch levers.

works corresponding to that of Fig. 1B. itlias been the practice to include normal and reverse contacts of the switch levers in series with the contacts of the normal and reverse switch indication relays so as to check the switch lever positions in these circuits. It is obvious that the switch levers for the switches of an established route, although inactive, may be inadvertently operated, and if their contacts were included in a route circuit the route check relay connected thereto over a reversed signal lever could be picked up or released by the operation of any7 of In the arrangement shown herein, this is not the case, and when a route relay such as relay ZRGS is energized, it maintains the continuity of the route circuit over which it is picked up and to which it is reconnected upon the release of relays ZRHK and ICK, and its release therefore is dependent, not only upon the reception of a code indicating that it is proper to cancel the route, but also upon the return of the controlling signal lever to its normal position.

Assuming now that signal 2RC has been cleared for a movement over the route extending to signal 6R, by the series of operations Vabove described, it is to be understood that the operator will also clear signal 6R to extend the route to signal 6L, by moving lever BSG to the right and pressing button SSTB, but since the resulting operations are similar to those already described, they will not be described in detail.

It will be, assumed that the starting relay OI ST button ISTB, with channel 'I energized, is ef' fective to maintain relay ZRHS reversed, provided it is received before the train governed by signal ZRC enters section IT, whereupon relay ZRHS is restored to normal and held normal by relay ITKR until a track occupied indication is transmitted as already described. If relay ITKR fails to restore relay 2RI-IS to normal, due to a fault, relay 2Rl-IS may be operated by code to its normal position, when relay ITKR is released. Signal ZRC is put to stop by the opening of contacts a' and c of relay ZRHS, in the circuit for its mechanism ZRCG, Fig. 2B, reenergizing relays 2RGP and ZRAS. In the indication code which follows these operations, channel III is supplied with current by relay ITKS, while channels I3 and I5 are open, and as a result of the transmission of this code, relay ITKR is reenergized over back contact b of relay ITKS if the transmission occurs while section I'I'- is occupied, or over front contact g of relay ITR if its transmission is delayed until after section IT is vacated. Relay ITKR completes a stick circuit at its contact a whereby it is held energized independently of relay IST. It follows that the signal control relay is placed in condition to be reoperated to reverse by a control code, as soon as an indication of the occupancy of the controlling track section has been transmitted to the oflice. In response to this indication code, relay ITK is energized over channel I0 to light the red lamp I'IKE on the track diagram, and a circuit is closed momentarily from channel I0'to wire 2I to pick up relay I--'ITKA, Fig. 1F, as hereinbefore described, and'relay l-l'IKA is then held energized'over a stick circuit including the right-i hand contact a of leverAZSG, disconnecting this lever contact from channel 1. Relay ZRHK is released by this indication code, closing a circuit assayed.

21 at its back contact d, Fig. 1C, for lighting the red lamp ZNE steadily and also closing a circuit at its back contact` c for causing lamp ZRE to flash until relay ZRGS is released by restoring lever ZSG to normal.

Even though this flashing indication is disregarded or fails to be properly displayed, so long as the signal lever ZSG is left in its reverse position, a control code initiated by the operation of relay OIST after the track occupied indication has been received would find channel 1 held open by relay ITKA.

It will be seen that after a signal has been put to stop by a train, it can be cleared for a second train by restoring its lever'to normal, to release the relay TKA, and then reversing it again before initiating the control code for controlling the signal. Since relay ZRHS is operable to reverse with section IT occupied, provided an indication of its occupancy has been transmitted to the oiiice, it may be that a second indication code, indicating that the signal has been recleared for a second train, will find relay ITK already in its energized position, but relay I`1TKA will not become reenergized over channel I because back contact b of relay ITK is open. It follows that if the control code for reclearing the signal is repeated, channel 'I remains energized and the code is effective to maintain relay ZRHS reversed.

Assume now that the movement of only one train over the established route is to be considered, and that a conflicting route is to be established as soon as this is vacated. The release of the route check relay 2RGS when the train enters the first section of the route releases the locking circuits at the oilice so that the operator is free to transmit switch operating codes, although in the field, each switch remains locked with its control relay WR non-responsive until the corresponding track section is vacated and the switch locking relay LR for that section is reenergized. The operator is of course able to avoid the transmission of switch control codes prematurely, making it necessary to repeat them, by observing the lighting of the track occupancy lamps in the track diagram. It may be, however. that a switch will remain locked when the corresponding track section is unoccupied' due to a fault in the wayside locking circuits and to enable such faults to be more promptly detected it is of advantage to indicate the condition of the locking relays LR directly, as may be readily accomplished by including in the indication system of Figs. 1H and 3A, the lock indication relays LK controlled over channel I4, as shown in Fig. 6A.

Assuming that these additional indications are included in the rst form of the apparatus, the operation of which has just been described, it will be understood that each relay LK controls a red lamp LE, mounted above the corresponding switch lever in Fig. 1A and controlled as in Fig. 7, and that the locking circuits including wires 3I--34 in Fig. 1H are modified to include contacts of the lock indication relays therein, as shown in Fig. 6B.

With this modification of the apparatus, the operations involved in clearing signal 2RC `for a movement over the route extending to signal 6R are similar to those already described except that relay ILK will be energized by the code which indicates the response of the signal to the control code for clearing it, thereby lighting the switch lever lamp ILE, and the locking relay SLR upon releasing will initiate a second indication code' by which relay SLK is energized to light lamp 3LE. Front contacts b of relays ILK and 3LK, Fig. 6B, supersede or supplement front contacts e of relays ZRGS in holding relays INWK and 3RWK energized, in Fig. 1H, after these indications are received. Relay ILK is released by the indication code transmitted when section IT is vacated, provided relay ILR becomes energized, and when released permits relay INWK to be released by reversing lever ISW and pressing button ISTB. Relay SLK remains energized to prevent the release of relay SRWK until an indication is received that section 3T is vacated and relay SLR is reenergized. It follows that the relays LK serve to prevent the operator from issuing a control code for the operation of a track switch unless the locking conditions permit the switch to respond and an indication of that fact has been registered at the control oiiice.

1t will next be assumed that the apparatus of the first form of our invention has been restored to its normal position as shown and that the operator moves lever ZSG to the right to clear signal ZRA. Relay ZRGS Will become energized at once over the route circuit o-f Fig. 1B which includes contacts b of the switch indication relays INWK, SNWK, SNWK and TNWK, and in Fig. 1H, contacts e and f of relay ZRGS connect terminal C` to wires 3 I-34 to maintain each of these switch indication relays energized, and in response to the operation of button ISTB, a control code is transmitted to reverse relay ZRHS and thereby energize mechanism ZRAG, Fig. 2B, over a branch of a circuit for the corresponding route which includes front contacts b of the track relays I TR, TTR and ZTR. lf any of these sections is occupied, signal ZRA will remain at stop and a stop indication will be returned, lighting lamp 2NE and also causing lamp ZRE to flash. The operator may now clear signal ZRC for this route by operating buttons ZCO and IS-TB, with lever ZSG in its right-hand position to reverse relay ZCO'S', which by closing its contact a, Fig. 2B, completes a circuit for mecha- Y nism ERCG. Lamp ZRE is extinguished by relay ICK when this control code is initiated, and becomes steadily lighted in place of lamp ENE when the return indication is received.

If now sections IT, 'IT and 2T become vacant, mechanism ZRAG becomes energized in multiple with mechanism ZRCG and energizes relay ZRAGP, Fig. 2C, which opens the circuit for mechanism ZRCG, thereby clearing signal ZRA in place of signal 2RC".

The operation of the second form of our invention employing the control panel of Fig. 5A will now be described, assumingr rst that the lock indication relays of Fig. 6A are not provided.

In this form of the invention all of the lever lamps as well as those on the track diagram are normally dark, and the only lamps lighted at any time are those relating to the routes which have been set up or which are being established.V In other Words the only lamps lighted are those which are directly of interest to the operator, and the manipulation of the plant is facilitated because the lamp indications are thereby rendered more distinctive than in a conventional panel in which large numbers of similar lights are continuously displayed.

It will rst be assumed that the crossover SAW-SBW is to be reversed and signal ZRC is to be cleared for a movement over the route extending to signal 6R as hereinbefore described. In this form of the apparatus, when lever SSW 

